B. Sutisna, G. Polymeropoulos, E. Mygiakis, V. Musteata, K.-V. Peinemann, D.-M. Smilgies, N. Hadjichristidis, S.P. Nunes
Polym. Chem., 7, pp. 6189-6201, (2016)
A poly(styrene-b-tert-butoxystyrene-b-styrene) copolymer was synthesized by anionic polymerization and hydrolyzed to poly(styrene-b-4-hydroxystyrene-b-styrene).
Lamellar morphology was confirmed in the bulk after annealing.
Membranes were fabricated by self-assembly of the hydrolyzed copolymer
in solution, followed by water induced phase separation. A high density
of pores of 4 to 5 nm diameter led to a water permeance of 40 L m−2 h−1 bar−1 and molecular weight cut-off around 8 kg mol−1.
The morphology was controlled by tuning the polymer concentration,
evaporation time, and the addition of imidazole and pyridine to
stabilize the terpolymer micelles in the casting solution via
hydrogen bond complexes. Transmission electron microscopy of the
membrane cross-sections confirmed the formation of channels with
hydroxyl groups beneficial for hydrogen-bond forming sites. The
morphology evolution was investigated by time-resolved grazing incidence
small angle X-ray scattering experiments. The membrane channels reject
polyethylene glycol with a molecular size of 10 kg mol−1, but are permeable to proteins, such as lysozyme (14.3 kg mol−1) and cytochrome c (12.4 kg mol−1),
due to the right balance of hydrogen bond interactions along the
channels, electrostatic attraction, as well as the right pore sizes. Our
results demonstrate that artificial channels can be designed for
protein transport via block copolymer self-assembly using classical methods of membrane preparation.